When I saw that you were talking Middle School, that got me to thinking about my Grandkids and what they liked at that age. They weren't interested in my "old-fashioned" little blocks all cut up. They were more interested in fabrics they could identify with, bright/bold and modern patterns. They, also, loved the idea of making pictures for a quilt....crayon type drawings.
I go to the Houston International Quilt Festival almost every year. The booths that seem to get the attention are the ones where people of all ages are drawing on fabric and creating their own works of art. Perhaps if you had a crayon quilt on display and got them to help create some blocks that you could stitch together later, you could get some creativity going. Maybe even a handout with instructions on how to make their own blocks, which could be incorporated into covers for iPads, laptops or even small purses.
Along the modern quilt theme...how about a quilt that includes the school mascot or some of the sports that they are involved in? It's all about catching their interest. Is there a wearable pattern that is super easy that would appeal to them? Are you interested enough in this project to offer classes to them during the summers? I would bet that not many of them even have sewing machines in their homes. Even if they showed an interest, would it get them anywhere?
And, I have to say, I am so glad that you are offering quilting to them. More may be interested than you really realize. My sister taught a gifted program in one of the local school districts. She had elementary children - grades 1-5. As one of her projects, she introduced them to making quilted potholders. She said that it was one of the most fun thing the kids did and they absolutely loved these small projects. Most had never had any access to a sewing machine and found it fascinating. I often wonder if it sparked a lifelong interest in sewing for any of these kids.